This invention relates to universal joints and, more particularly, to a lubrication system for a universal joint cross assembly.
Universal joints are well known devices which provide a driving connection between two members adapted to rotate about non-aligned axes of rotation. A typical universal joint structure includes a cross having a central body portion with four cylindrical trunnions extending outwardly therefrom. The trunnions are oriented in a single plane and extend at right angles relative to one another. A hollow cylindrical bearing cap is mounted on the end of each of the trunnions. Needle bearings or similar means are provided between the outer cylindrical surfaces of the trunnions and the inner cylindrical surfaces of the bearing caps to permit relative rotational movement therebetween.
During operation, the first and second members, as well as the universal joint connected therebetween, rotate as a unit. Whenever the axes of rotation of the first and second members are not coaxially aligned, a small amount of oscillating rotational movement occurs between each of the bearing caps and the trunnions upon which they are mounted. To prolong the life the bearings, a lubricant is provided in each of the bearing cups. Some type of seal is typically provided to retain the lubricant and prevent the entry of dirt into each of the bearing cups.
Certain universal joints are provided with lubrication provisions which allow for the addition of lubricant to the bearing cups without requiring the removal and reinstallation of the bearing cups. Heretofore, with universal joints having such lubrication provisions, a cross body had a central lubricant fitting with the cross body having passages extending outwardly from a central point directly to each of the bearing cups. With such a system, there is no way of knowing whether each of the bearing cups and bearings received proper lubricant if, for example, lubricant was blocked by air pockets, obstructions, etc. This problem may be compounded by the increasingly tight bearing cup seals being utilized, which are more effective in preventing the entry of dirt into the bearing cups, but which further inhibit the purging of air during the introduction of lubricant.
In addition, with the conventional universal joint having the described lubrication provision, lubricant is typically added until excess lubricant escapes from about the open end of one or more of the bearing cups. This results in the uncontrolled discharge of the lubricant into the environment.